This invention concerns a method for separating a broken warp thread at the warp stop motion from the warp sheet on a weaving machine--in particular on weaving machines of the type in which the warp stop motion consists of one or more rows of drop wires--in order to enable the broken warp thread to be automatically located and taken up. The invention also concerns a device which uses this method.
A warp stop motion commonly used on weaving machines consists of a row of drop wires resting on the warp threads, so that when a warp thread break occurs, the corresponding drop wire makes an electrical contact or mechanical interlock, thus causing the machine to be stopped.
Dutch patent application No. 8600372, which corresponds to the U.S. Pat. No. 4,791,967 to Vandeweghe, et al., issued on Dec. 20, 1988, describes a method of automatically locating the fallen drop wire, which is then gripped and raised in order to make it visibly stand out from the row of drop wires, thus enabling the weaver to see at a glance where a thread break needs to be repaired. Dutch patent application No. 8601819 which corresponds to U.S. Pat. No. 4,815,498, issued on Mar. 28, 1989, also describes a method for turning the fallen drop wire through an angle so that the neighboring drop wires are forced apart, thus forming a local opening in the unbroken warp threads, and so facilitating rethreading of the drop wire which is presented in this way.
Although the abovementioned patent documents are aimed at automating the process of warp thread repair, they do not offer any solution to the problem of dealing with the broken warp thread, which is usually still threaded through the fallen drop wire, either by removing it and replacing it with a new one or by tying it in again. The problem is mainly that the broken warp thread which remains threaded through the fallen drop wire first has to be located, which is fairly difficult to automate since the warp thread which was under tension contracts when it breaks and gets crossed over neighboring threads.